International Patent Application No. WO 2006/072514 A1 describes a pencil-type glow plug has an integrated pressure sensor. The pressure sensor in the conventional pencil-type glow plug is connected to a rod-shaped heating element that is accommodated in movable fashion in the interior of the pencil-type glow plug. A steel diaphragm having a radially symmetrical construction is allocated to the rod-shaped heating element; said steel diaphragm shields a force-measuring element of the combustion chamber pressure sensor against combustion gases, and has a spring elasticity that is a function of its geometry.
The pencil-type glow plug described in International Patent Application No. WO 2006/072514 A1 has the disadvantage that the hot combustion gases that occur during each working cycle cause a heating of the steel diaphragm, followed by a cooling of the steel diaphragm, so that the pressure measurement is impaired due to thermal changes in length of the steel diaphragm. Specifically, the conventional pencil-type glow plug having the integrated pressure sensor has the disadvantage that a distortion of the outputted pressure signal occurs.